Answer:
A buyer's willingness to pay for a good plus the price of the good means the buyer is indifferent between buying the good and not buying it.
Surplus is the amount by which the quantity supplied of a good exceeds the quantity demanded of the good.
Producer surplus is the amount a buyer is willing to pay for a good minus the cost of producing the good.
Consumer surplus is the amount a buyer is willing to pay for a good minus the amount the buyer actually pays for it.
